Surface molecules and chemisorption. II. Photoemission angular distributions

Abstract

A theory of the angular distributions of electrons photoemitted from submonolayer films of chemisorbed atoms is presented. Chemisorption is treated within the surface-molecule limit of the Anderson model. It is shown that the key features which differentiate between solid-state photoemission and atomic photoionization are the localization of the hole left behind in the photoexcitation process and the preferential orientation of atomic or molecular orbitals (in photoemission from solids or chemisorbed atoms). The differential photoionization cross sections or angular distributions for spatially oriented atoms and surface molecules are obtained and contours of constant emission intensity, as projected on a flat fluorescent screen which is parallel to the surface, are presented. It is shown that the chemisorption bonding geometry can be ascertained from such measurements.